The present invention relates to an aiming guide for use with an X-ray or other radiation source for accurately positioning a trocar or drill over the holes in the distal end of an implanted intramedullary nail and drilling through such holes and the surrounding bone material.
Intramedullary nails are used to aid in the healing of fractured bones. A nail is implanted in the medullary canal of the bone across the fracture site in order to position the bone fragments and provide load-bearing support so that the patient can move about while the bone is healing. The nail is secured to the bone by a series of locking screws or fixation bolts, which must pass through holes in the nail and into the surrounding bone material.
After the nail is inserted into the medullary canal, the distal end of the nail is no longer visible to the eye. The nail can be viewed with the use of an X-ray or other radiation source because it is constructed of stainless steel or other radiopaque material. The nail will cast a dark, elongate image on the X-ray monitor, while the nail holes will appear as light circles or ovals. In particular, a nail hole will appear as a circle when the X-ray source is positioned such that the X-ray beam is parallel to the axis of the nail hole.
In order to secure the nail to the bone, a trocar or scalpel is used to make an incision through the soft tissue to the bone material, and a drill is used to drill through the nail hole and surrounding bone material for insertion of the locking screw. An aiming guide is used with the X-ray source in order to accurately position the trocar and surgical drill over the nail holes.
Various aiming guides are already known in the art, such as those disclosed in U.S. Pat. Nos. 4,969,889, 4,917,111, and 5,478,343. In general, each of those devices has a handle portion constructed of a radiolucent material, such as plastic, which is relatively invisible to X-rays and thus will not cast a strong image on the X-ray monitor. Certain radiopaque aiming components, such as metal rings or other structures, are attached to or located within the distal end of the radiolucent handle. The radiopaque components will cast a definite image on the X-ray monitor when the X-ray source is turned on. The aiming guide is then positioned over the nail in such a manner that the image(s) cast by the radiopaque aiming components is (are) superimposed over the circular image of the nail hole on the X-ray monitor. Once the aiming guide is properly positioned over the nail hole, a trocar is used to make an incision to the surface of the bone above the nail hole, and a drill can be used to drill accurately through the nail hole and surrounding bone material for insertion of the locking screws.
Certain aiming guides, such as that disclosed in U.S. Pat. No. 4,969,889, contain substantial radiopaque components and thus tend to be rather heavy and bulky. Other aiming guides, such as that disclosed in U.S. Pat. No. 5,478,343, require the simultaneous manipulation of more than one instrument in order to locate and drill through the nail hole. Also, the protection sleeves and trocars used in the prior art were constructed entirely or substantially of metal, which made them heavy and tended to obstruct the view on the X-ray monitor. A more compact, unitary, and lighter weight aiming guide having fewer radiopaque components would prove advantageous.
The present invention is a radiolucent aiming guide that is used with an X-ray source to accurately position a trocar or drill over a nail hole in order to make the incision and hole for insertion of a locking screw. The aiming guide has an elongate handle constructed of a radiolucent material to place the surgeon""s hands at a distance away from the area of the X-ray beam. A threaded hole, running perpendicular to the longitudinal axis of the handle, is located at each end of the handle. A hollow, cylindrical protection sleeve is screwed into one of the threaded holes in the handle. A protection sleeve is constructed substantially of a radiolucent material, with the exception of the tip at its distal end, which is made of metal or another radiopaque material that casts a dark image on the X-ray monitor. A trocar is inserted into the protection sleeve for making the incision to the bone. The trocar is constructed substantially of a radiolucent material except for the solid pointed tip at its distal end, which is constructed of metal or another radiopaque material. The radiopaque tip of the trocar will cast a dark image within the image cast by the radiopaque tip of the protection sleeve.
The aiming guide is positioned over the limb such that the longitudinal axes of the trocar and protection sleeve are aligned parallel to the direction of the X-ray beam. When the aiming guide is positioned in that fashion, the radiopaque tips at the distal ends of the protection sleeve and trocar will cast concentric circular images on the X-ray monitor. The aiming guide is moved until those concentric circular images are superimposed over the circular image of the nail hole, which indicates that the protection sleeve and trocar are in alignment with the nail hole.
The proper rotational alignment of the aiming guide with respect to the nail hole is checked by means of two radiopaque pins, which lie parallel to and on either side of the longitudinal axis of the handle near the threaded hole. Those two pins cast dark images on the X-ray monitor on either side of the image of the nail when the aiming guide is properly oriented with respect to the nail. Once the aiming guide is accurately oriented over the nail hole, the trocar is used to remove the soft tissue lying above the nail hole.
After the soft tissue has been scraped away, the trocar is withdrawn and replaced with a hollow, essentially cylindrical drill sleeve. The drill sleeve is constructed of a radiolucent material that does not cast an image on the X-ray monitor. A drill bit connected to a surgical drill is then inserted through the drill sleeve. The drill bit is constructed of a radiopaque material that, like the trocar tip, creates a solid circular image on the X-ray monitor when the longitudinal axis of the drill bit is aligned parallel to the X-ray beam. That image can be used to ensure the proper alignment of the drill bit with the nail hole. Once the drill bit is properly aligned, the drill bit is drilled through the nail hole and the surrounding bone material.
After the drill bit is drilled through the first nail hole, the bit is detached from the drill and left in place in the bone. The aiming guide and protection sleeve are removed and rotated, so that the proximal end of the drill bit, which is extending out of the bone, can be inserted through a small hole located in the handle of the aiming guide. The axis of that small hole is parallel to that of the larger threaded hole that secures the protection sleeve. The distance between the axes of the large and small holes in the handle is the same as the distance between the two holes in the distal end of the nail. Thus, when the handle, is reversed and the drill bit inserted into the smaller hole, the protection sleeve, which is located in the larger hole, is essentially aligned with the second hole in the nail. The concentric circular images cast by the protection sleeve and trocar on the X-ray monitor can then be used, as before, to ensure the proper alignment of the aiming guide with the second nail hole.
The protection sleeve and trocar are used, as before, to remove the soft tissue over the second nail hole. The trocar is then replaced with a drill sleeve and a second drill bit. The second drill bit is drilled accurately through the second nail hole and the surrounding bone material in the manner described above. The second drill bit and the drill sleeve are removed, and a locking screw is inserted through the protection sleeve and screwed through the bone and second nail hole to secure the nail to the bone. The aiming guide and protection sleeve are then repositioned over the first drill bit, which is still located in the bone and nail. The first drill bit is removed, and a second locking screw is inserted through the sleeve and screwed through the bone and first nail hole to secure the nail to the bone.